The mouthpiece of a single-reed woodwind instrument is a device upon which the vibrating reed element is normally mounted to a surface of the mouthpiece, so that the tapered, less-thick end of the reed, being very flexible, functions as a reed valve. The reed, which opens and closes an opening in the mounting surface of the mouthpiece, is in oscillatory cooperation with the vibrating air column of the instrument. The opening, more commonly known as the window, normally is positioned relative to the reed and so sized such that only the underside of the reed in the region of the tapering segment of the reed interfaces with the air column of the instrument via the tone chamber portion of the mouthpiece. A survey was made of prior art and it was found that the length of the window never exceeded 57% of the length of the reed for the alto saxophone mouthpiece, and somewhat less than 57% for other types of saxophones and clarinets.
The remaining segment of the reed that is untapered, known as the heel of the reed, is normally clamped against the portion of the mounting surface of the mouthpiece, known as the table. The clamping is effected by means of a device known as a ligature. While conventional ligatures are typically configured on the premise that the heel of the reed is not actively associated with the generation of sound, a variety of ligature designs have been patented which recognize that the heel of the reed is an integral part of the vibrating system, and the manner in which the heel is restrained will influence the tonal character, the body of the sound, and the playing response of the reed/mouthpiece system. U.S. Pat. No. 2,837,003 issued to Collis discloses such a ligature which has four corner points exerting pressure on an intermediate portion only of the reed and the mouthpiece beneath the reed, permitting the reed to vibrate freely from air blown into the mouthpiece.
Another aspect of the design of the mouthpiece that influences tonal quality and playing response is the tone chamber and bore configuration. The tone chamber section of the mouthpiece is principally an acoustic transformer which converts the higher acoustic impedance at the tip of the mouthpiece to a lower impedance at the interface with the bore of the mouthpiece. Both the chamber and bore geometry can be configured in endless ways to achieve desired tonal colorations. One of the disadvantages of contemporary mouthpiece design is, that in an attempt to achieve certain tonal characteristics, proper impedance matching is often compromised, thus affecting power and response. Abrupt changes in cross-sectional area are often found, which reduce energy transfer through the region. Typically, the steep slope of some chambers or the abrupt expansion in cross-sectional area from the chamber to bore of other mouthpiece types, in conjunction with the bore-to-neck reduction in cross-section area of saxophone mouthpieces create a low-pass acoustic filter not unlike that of automobile mufflers or gun silencers. In the acoustic configuration of the prior art, it can be noted that such mouthpieces are typically configured with abrupt changes in cross-sectional areas or steep slopes in the chamber region. The enlargement formed by the bore of the mouthpiece between the end of the neck (leadpipe) and the abrupt reduction in cross-sectional area at the bore end of the chamber is what forms an acoustic filter. Such filtering induces a muffled tonal quality, reduces tonal dimension and projection, and diminishes the response of the instrument to the player.
While the design of mouthpiece chambers have been explored in countless ways, the bore has received little attention, typically having a straight or slightly tapered cylindrical geometry. This form of unidimensional geometry does not offer the more complex tonal color that is available with alternative geometries. As noted in the third edition of "Fundamentals of Acoustics" by Kinsler, Frey, Coppens, and Sanders published by Wiley, in Chapter 9, regarding resonance in pipes, cavities, and waveguides, the complexity of resonances for rectangular waveguides is greater than that for cylindrical waveguides.